Much audio, visual or audiovisual content, such as movies or motion pictures, consist of a linear sequence of events. Movies, for example, are distributed in a wide range of formats, such as digital cinema, optical discs and internet-based streaming formats. In digital cinema (e.g., IMAX), the movie is displayed in a theater on a large screen using very high (e.g., Ultra HD television) resolution. More recent formats use lower resolution. Optical discs (e.g., DVDs) often contain the movie rendered at HDTV resolution. Internet-based streaming formats traditionally use standard-deviation television (SDTV) resolution.
Optical disc formats can support multi-viewpoints or versions (called “angles”) of at least certain scenes of the movie, although this feature is not widely used. The viewer or end-user has the ability to select one of multiple viewpoints in a way that resembles channel selection in broadcast TV networks.
U.S. Patent Application Publication No. 2014/0019767 describes the Irdeto Tracemark® fingerprinting technologies. This application describes the use of content sections that include different watermarks, where the receiver/player selects one of these sections during rendering. A sequence of such differently watermarked sections in the content forms a fingerprint in the output that can be traced back to a specific player or a group of players. Such technology is used in broadcasting, on pre-recorded media (e.g., DVD and BD+), and in live streaming Internet Protocol television (IPTV).
Movie, and other conent, distribution generally uses some form of media protection to prevent the unauthorized redistribution of the digital content. This often requires the encryption of the digital content, which is decrypted and further processed in a trusted functional module within the display, or other type of rendering equipment. The trusted module contains secret data such as cryptographic keys. Examples of such modules are Digital Rights Management (DRM) modules and Conditional Access (CA) smart cards. Such modules rely on tamper resistance to ensure the functional integrity of the modules.
Optical discs typically use protection techniques (e.g., Content Scramble System (CSS) and Advanced Access Content System (AACS)) that encrypt the content with a content encryption key which is stored on the disc in encrypted form. The processing to decrypt the content requires protection against a so-called “whitebox” attack scenario. Known protection schemes are hardware tamper resistance techniques and software obfuscation (e.g., such a system is disclosed in U.S. Pat. Nos. 6,594,761 and 6,842,862 (“whitebox cryptography technology”)).
Computer games use short, movie-like fragments in between different “levels” or “stages” during gameplay that are rendered using the game engine. Game consoles also rely on DRM techniques to protect against unauthorized distribution (e.g., cloning of the disc content).
As shown in FIG. 1, traditional (audiovisual) content includes a linear sequence of content parts Pi, Pi+1, Pi+2, Pi+3, etc., as shown in FIG. 1. Typically, each content part Pi, Pi+1, Pi+2, Pi+3, etc., contains a sequence of images that forms a certain time period, such as a second, of content. Each content part Pi, Pi+1, Pi+2, Pi+3, etc., thus forms a random access point into the content. Often, content parts Pi, Pi+1, Pi+2, Pi+3, etc., are encoded in a way that enables decoding to start efficiently at the beginning of the content part. An example of this type of content encoding is MPEG 2.
The Tracemark® fingerprinting technologies duplicate one or more content parts, associate a different watermark with each copy, and place or insert the results into modified content, as shown in FIG. 1A. In particular, FIG. 1A shows two alternatives for the content part Pi+1 and the content part Pi+3. The content viewer or player selects one of the alternatives during playback. This results in an output stream with a single marked set of content parts. If each marking carries a single bit of information (P0 or P1), the output sequence for the short sequence of content parts in the figure carries two bits of marking information. Richer and denser marking information can be achieved by longer sequences of replacement content parts or by including more duplicate versions for the replacement content parts.
U.S. Patent Application Publication No. 2011/0211695 (Westerveld) describes a variant of the above scheme, where the selection of the content parts is implemented by the error correction module in the player or receiver. Each of the two differently watermarked content parts (P0i+1 and P1i+1) is encrypted differently (e.g., using a different key). As both these content parts are decrypted similarly (using the same key and algorithm), one of the versions will be converted into random data. This random data then is removed by the error correction module. This makes it possible to perform the watermark selection without requiring special switching logic in the player, which makes this technique applicable to legacy players.
Great Britain Patent Application Publication Nos. 2424351 B (Ingrosso) and 2470617 A (Abram) describe polymorphic content formates that consist of alternative content parts, as shown in FIG. 2. In particular, FIG. 2 shows at least one or multiple alternatives for each content part Pi, Pi+1, Pi+2, Pi+3, etc. Each alternative contains different content (e.g., encoded material). At the boundaries of the alternative content parts, the content allows for transitions to other alternative content parts. For convenience, the content parts are shown as having equal length, although in practical implementations, the duration of alternative content parts can vary significantly. The player may select between the variants to generate a unique version of the content, as shown in FIG. 4.
Ingrosso describes a player architecture, as shown in FIG. 4. In particular, FIG. 4 shows the polymorphic movie content that is contained on a pre-recorded optical disc (e.g., a DVD). In addition to the normal audio and video data, the optical disc contains metadata describing the available alternative content parts. The metadata is stored in a polymorphic movie data base, which is used to generate a sequence of alternative content parts that form a valid content output. Ingrosso describes various details that constrain the sequence generation to meet various creative and logical conditions for a valid output sequence. During playback a pseudo random number generator is used to trigger one of the possibly many different output sequences.
It is well known to alter presentation of content in an interactive game in response to user inputs during the game play. For example, U.S. Pat. No. 8,668,563 (Reynolds) discloses a gaming engine which a user controls actions of a character in game play. FIG. 6 shows a game engine as disclosed by Reynolds.